The present invention generally pertains to servo systems and is particularly directed to a system for continuously controlling a servo motor in response to a digital command signal.
In controlling a continuously controlled analog output device, such a servo motor, in response to a digital command signal, a digital-to-analog (D/A) conversion must take place somewhere in the system. The D/A conversion inherently causes phase lag because of the discreet interval sampling process which occurs at a digital signal processor frame rate, even when the D/A conversion is performed within the servo loop; and therefore the sampling phase lag adds directly to system errors. This phase lag is a serious difficulty against obtaining high performance in digitally controlled systems, such as in the implementation of digital controllers to meet tactical missle guidance and control requirements.
It is an object of the present invention to provide an improved digitally controlled servo system wherein the phase lag is reduced significantly to enable the system to be used in missle applications, with high performance, low power drain, and minimum cost.